#include using namespace std; typedef long long ll; typedef pair pii; #define FOR(i,a,n) for(int i=a;i<(int)(n);i++) #define REP(i,n) FOR(i,0,n) #define ALL(a) (a).begin(),(a).end() #define MP(a,b) make_pair(a,b) #define PB(a) push_back(a) #define F first #define S second const int INF = 2000000000; const int DX[4]={0,1,0,-1}, DY[4]={-1,0,1,0}; struct P{int x;int y;P(int X=0,int Y=0){x=X;y=Y;}}; int main() { int x1,y1,x2,y2; cin >> x1 >> y1 >> x2 >> y2; int x=0,y=0; int ans = max(abs(x1),abs(y1)); if(abs(x1) == abs(y1)) { if(abs(x2) == abs(y2)) { ans++; } } cout << ans << endl; return 0; }